Watering question?

My plants are going on three months old and are flowering. I have noticed looks to be some nutrient deficiency on some of them so my question is is can I give them straight water for a day or two to see if it helps then go back to water with nutrients? My guess is that they have 2-4 weeks left before harvest time. Thanks in advance for all advice.

you look like you have a deficiency so want to know if you can use plain water then back to feeding? sorry this doesn't make sense